JPS61117735A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To shorten the transient response delay of a servo system at a switching time by opening the servo system to apply a preliminarily set bias voltage in case of switching to recording or reproducing and performing the control by the servo system after stabilization. CONSTITUTION:In an optical disc recording and reproducing device, laser power is normally monitored by a photodetector 22 and is fed back by the servo system to control the bias voltage. In case of switching from reproducing to recording, high-speed switches 15, 21, and 23 are switched to prescribed positions, and a preliminarily determined reference voltage V2 is inputted to a laser power control circuit 5 through a differential amplifier 19. When the servo system is stabilized thereafter, the high-speed switch 21 is switched to control the bias voltage by the servo system. In case of switching to reproducing, the same operation is performed. Thus, the transient response delay of the servo system is shortened in case of switching to recording or reproducing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical recording/reproducing device eK, e! ! fVc Q
The present invention relates to a control circuit suitable for controlling laser power during time and reproduction.

[Background of the invention]

BACKGROUND ART Conventionally, in an optical disk recording/reproducing apparatus, as a method of dealing with fluctuations in laser power due to temperature changes, there has been known a method of controlling the laser power by feeding back the laser light and detecting the laser power. (Unexamined Japanese Patent Publication No. 55
(No. 122240) However, when the disk is rotated at a constant angular velocity, the laser power must also be controlled in accordance with the recording position in the disk radial direction in order to maintain a constant energy beam density during recording. .

At the same time, when recording high-density digital signals on a disk, the above-mentioned laser power control is required, as well as switching response and feedback servo system transient response when performing recording to playback and playback to recording. There was a problem with the need to minimize delays.

[Purpose of the invention]

An object of the present invention is to provide optimum laser power control for any position on a disk when digital information is reproduced using a laser beam on concentric or spiral tracks of a disk-shaped medium. It is an object of the present invention to provide an optical recording/reproducing device which reduces the transient response delay of laser power when performing recording to reproduction or reproduction to transition.

[Summary of the invention]

In order to achieve the above object, the present invention forms a servo loop that controls laser power according to temperature, recording position, and recording or reproducing in an optical disc recording/reproducing device #, and feeds back laser light to reproduce from recording. , or when switching from playback to recording 4: When switching from playback to recording when controlling the bias voltage based on the respective reference voltages (open the servo loop and instead use the first prerecorded applying a bias voltage set for the control circuit to the control circuit, closing the servo loop after the thread of the open servo loop becomes stable to control the bias voltage, and opening the servo loop when switching from recording to playback;
Instead, a second preset bias voltage for regeneration is applied to the control circuit, and the servo loop is closed to control the bias voltage after the thread of the open servo loop has stabilized.

Hereinafter, the principle of the present invention will be explained in detail using the drawings.

The Mi diagram is a basic configuration block diagram of an optical recording/reproducing device. In FIG. 1, 1 is a recording signal input terminal, 2 is a modulation circuit, 3 is a bias voltage input terminal, 4 is a modulation signal voltage input terminal, 5 is a laser power control circuit, and 6 is a laser drive circuit.

7 is a laser light source, 8 is an optical system for laser light control, 9
1 is a disk-shaped recording medium, and 10 is a motor for rotating the disk-shaped recording medium at a constant speed.

Here, we will discuss the operating principle of laser power control in the second section.
This will be explained using figures. FIG. 2 (α) shows the static characteristics of bias voltage versus laser power.As the bias voltage v0 increases, the laser power fl P.

become. A voltage v0 is applied to the bias voltage input terminal 5 of the laser power control circuit 4, and a recording signal is input from the terminal 1, and the waveform after passing through the modulation circuit has a peak voltage of V as shown in FIG. 2(b). , then input this signal to the laser power control circuit, the laser power will be as shown in Figure 2 (
As shown in C), the power is modulated according to the recording signal from 5 KP to P, and after passing through the laser drive circuit 6.

It is emitted from a laser light source 7.

In a device having such a configuration, a bias voltage ■ is applied to the bias voltage input terminal 5. , and the peak voltage v is added to the modulation signal voltage 4.
When a signal of 1 is input, the laser power is modulated according to the recording signal. The disk-shaped recording medium 9 is
When the laser power exceeds the recording threshold power between A and B in FIG. recorded as a pit on top. During reproduction, the laser power is between A and C in FIG. 2 (eL).

The reason for changing the bias voltage between recording and playback is to change the bias voltage during recording rather than during playback so that the laser power can have a thermal effect even at a low level of Pl, and to make it easier to record at a time when the laser power is higher than that. Bias voltage is increased.

Therefore, when feedback control is performed for bias voltage control as described in 5 above, a bias voltage transient response delay occurs when switching from recording to reproduction or from reproduction to recording.

This is because the bias voltage relative to the average voltage of the recording signal changes during recording.

On the other hand, depending on the recording modulation method, the maximum and minimum values of the average voltage of the recording signal can be defined. For example, MFM (Mtyd
ifiatt Fraqwgney MocLulat
iots) method, if the data bit interval is T, the minimum inversion interval of the modulated signal is T, and the maximum inversion interval is 2.
It becomes T. Therefore, in this combination, the minimum average voltage is the combination of patterns shown in Figure 3 (α)K, and when the pulse changes from 0 to vH, the average voltage is dVH, and the maximum average voltage is Figure 5 (h ) When the combination of K display patterns is used, the sono average voltage becomes negative vH.

Therefore, when switching from playback to recording, first open the feedback loop, input the bias voltage expected from the modulation method and recording signal pattern to the bias voltage input terminal 4 as described above, and then feed back after a certain period of time. Close the loop. In this way, the change in the bias voltage before and after closing the feed loop is small, and the transient response delay to the bias voltage when switching from reproduction to recording or from recording to reproduction can be reduced.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. Fourth
The figure is a block diagram of the configuration of an optical disc recording and reproducing apparatus according to the present invention.

In this figure, parts with the same numbers as in FIG. 1 have the same functions as in FIG.

11 is an input terminal for the voltage corresponding to the recorded position on the disk, 12.15 is an amplifier, 1, 18. 19 is a differential amplifier, j, 5, 21, 25. 21 is a high-speed switch, 16
1 is an input terminal for the reference voltage V during reproduction, 17 is an input terminal for the reference voltage V during recording, 20 is a Ronox filter, 2
2 is a light receiving element for laser power monitoring.

First, the case of reproducing a signal recorded on a disc will be described.

In this case, in the +S high-speed switches 15, 21, and 221C, α, tt and f, and f and i are conductive, respectively. At this time, the reference voltage ■ is inputted to the positive terminal (input) of the differential amplifier 14, and the negative terminal is grounded. This differential amplifier 14 is for controlling the reference voltage and the laser power for the recording position. However, during a lifetime, a constant amount of laser light is reflected no matter where on the disk the laser light hits (therefore, there is no need to keep the energy density constant;
There is no need to control the laser power for a reproduction position of 1 m1K. Therefore, the negative input of differential amplifier 14 is grounded. The output then enters the positive input of the next differential amplifier 18.

The output of the laser power monitoring light receiving element 22 is input to the negative input of the differential amplifier 18.

This light-receiving element 22 converts the power of the laser beam fM7 into a power laminate pressure. Therefore, as the laser power increases, the output voltage also increases, and as the laser power decreases, the output voltage also decreases. Therefore, for example, if the power of the laser emitted from the laser light source fluctuates due to temperature, etc., when the laser power increases, the output of the differential amplifier 18 is a voltage that decreases the laser power, and conversely, the laser power decreases. Differential amplifier 1
The output of 8 is controlled to increase the laser power.

In other words, the power of the laser is monitored by the light receiving element 22, and the power is fed back for control.

The output from the differential amplifier 18 controlled in this manner enters the low-pass filter 20, and only the low frequency component of the output from the differential amplifier 18 passes through the high speed switch 21 and then enters the laser power control circuit 5. However, in this case, the terminal IK recording signal is not input, so power modulation is not performed by the recording signal. The output of the laser power control circuit 5 enters the laser drive circuit, undergoes voltage-to-current conversion, and causes the laser light source 7 to emit light.

The laser beam output from the laser light source passes through an optical system 8 for controlling the laser beam, and then passes through a disk-shaped medium 9.
corresponds to The reflected or transmitted light is captured by another optical system (not shown) as a reproduction signal. Furthermore, as mentioned earlier, the KL/- laser beam also enters the light receiving element for laser power monitoring.

The above is a method for controlling laser power during reproduction. Next, the case of switching from reproduction to recording will be described.

First, the high-speed switches 15, 21, and 25 are switched, and α and e, a and f, and le and t are brought into conduction. Also, before these switches are switched, the high speed switch 240 is electrically connected.

First, a voltage corresponding to the recording position (radial direction of the disk) K is inputted to the terminal UK. This voltage is lower toward the outer circumference, and higher toward the inner circumference. After passing through amplifiers 12, 15, this voltage enters the respective negative terminals of differential amplifiers 14.19. Therefore, the output voltage of the differential amplifiers 14 and 19 is controlled so that it is low when the recording position is on the inner circumference, and high when the recording position is on the outer circumference.

When switching from playback to recording, the reference voltage V at the time of recording is input to the positive input of the differential amplifier 19 by the switch operation as described above, and the bias voltage input terminal (the input voltage is increased, but the bias voltage at this time is is set to a voltage that corresponds to the modulation method of the recording signal.Also, this bias voltage is controlled like the recording position in 5 above.At this time, the realization time of the bias voltage is is only delayed by the high-speed switches 21, 24 and the differential amplifier.Therefore, there is less transient response delay of the bias voltage, but this (Iasumi pressure) is not the average of the actual recorded signal.

At this time, the recording signal input to the recording signal input terminal 1 enters the modulation circuit 2, and the signal modulated by this circuit enters the laser power control circuit 5 through the modulation signal voltage terminal. Here, the modulation signal and bias voltage are used to convert the laser power into a signal that controls the laser power. The emitted light passes through the laser beam control optical system 8 and records the signal on a disk-shaped recording medium 9, and also enters the laser power monitor light receiving element 22. There, the signal is converted into a voltage corresponding to the laser power. enters the mica input of the differential amplifier 18.The output of the differential amplifier 18 passes through a low-pass filter, and after a certain period of time 1=1, the terminal d of the high-speed switch 21 becomes the same voltage as the bias voltage input terminal 4. There is.

Here, 1d1 passes through the above path after - and f of the high-speed switch 21 are connected, and a predetermined voltage is applied to the high-speed switch 21.
This is the delay time until the signal is output to terminal d.

Next, after 1d1 or more time has elapsed, 1 high speed switch 2
1 switches and d and f become conductive. Therefore, by configuring a feedback loop K, a bias voltage corresponding to the signal input from the modulation signal voltage input terminal 5 is input to the bias voltage input terminal 4.

At this time, the preset bias voltage does not exactly correspond to the signal input to the modulation signal voltage input terminal 5, but the maximum and minimum values of the average voltage of the modulated signal are limited by the modulation method. Therefore, the difference from the bias voltage corresponding to the actual modulation signal is small.

Furthermore, if the pattern of the first input signal in the input signal format is made into a fixed pattern over the time period tct, the bias voltage set in advance can be made the same as the bias voltage corresponding to the signal input to the modulation signal voltage input terminal 5. can be made into something.

Next, we will discuss the case of switching from recording to playback. First, the high-speed switches 15, 21, 25, 24 are switched,
α, − and f, y and ε, and j and l are electrically connected, respectively.

Since this cutting is switched to reproduction, there is no need to control the laser power for the reproduction position as explained in the section 5 regarding reproduction above. Therefore the differential amplifier 14.1
9 negative inputs each high speed switch 25.24
grounded by

In addition, the positive input button of the differential amplifier 19 is connected to the high-speed switch 1.
5, the reference voltage v1 is input, and the differential amplifier 19 outputs a bias voltage for sketching.

However, the output from the high-speed switch 210 (immediately after switching) takes time t4 for the output from the low-pass filter 20 to drop to a predetermined voltage due to the transient response of the system, just as during recording.

Therefore, as described above, until the output of the low-pass filter 20 reaches the predetermined bias voltage during reproduction,
A separate constant voltage source is supplied to the bias voltage input terminal 4, and after the output from the low-pass filter reaches a predetermined bias voltage, the high-speed switch 21 is switched, d and 1 are made conductive, the feedback loop is closed, and Try to stabilize the laser power used during subsequent playback.

As described above, when switching from playback to recording, a feedback loop of the mass laser power is opened, and the bias voltage expected from the modulation method or the recording signal pattern at the time of switching is first supplied, and the feedback loop is When the system becomes stable and a predetermined bias voltage can be supplied, the feedback loop is closed to stabilize the laser power thereafter.

Furthermore, reproduction can be controlled using a similar concept, and by using this circuit, transient response delay of the bias voltage can be reduced.

〔Effect of the invention〕

According to the present invention, it is possible to reduce the transient response delay of the bias voltage that controls the laser power when switching from reproduction to recording or from recording to reproduction.
This has the effect of reducing dropout, deterioration, or excessive recording of recording signals during the above switching.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of an optical recording and reproducing device.
Fig. 2 is a diagram for explaining the static characteristics and modulation method of a general optical modulator, Fig. 5 is a diagram for explaining the average voltage limitation due to the modulation method, and Fig. 4 is a diagram for explaining the laser power of the present invention. FIG. 2 is a block diagram of one embodiment of a control circuit. 1... Recording signal input terminal, 2... Modulation circuit, 5...
・Bias voltage input terminal, 4... Modulation signal voltage first terminal, 5... Laser power control circuit, 6... Laser drive circuit, 7... Laser light source, 8... Optics for controlling the laser source System, 9...Disc-shaped recording medium, 1o...Motor, 1
1... Voltage input terminal corresponding to the recording position on the disk, 12... Amplifier, 15... Amplifier, 14...
Differential amplifier, 15...High speed switch, 16...Reference voltage input terminal during playback, 17...Reference voltage input terminal during recording, 18...Differential amplifier, 19...Differential amplifier , 2a...Low pass filter, 21...High speed switch, 22...Light receiving element for laser power monitor, 25
...High speed switch, 24...High speed switch.ゎOh/19-t: Ah, eh ( 1st closed% 2 z 3 mouth (b> 箪 4)

Claims (1)

[Claims] 1. In an apparatus that uses a laser as a light source and records and reproduces information on concentric or spiral tracks of a disk-shaped recording medium rotating at a constant rotational speed, a bias voltage is used as a parameter. , a control circuit that changes the power of the laser, and a bias that monitors the light emitted by the laser and forms a laser power control servo loop and applies it to the control circuit in order to keep the laser power irradiated to the disk constant. A circuit for setting a voltage, and the servo loop is opened when switching from playback to recording, and instead, a first bias voltage set in advance for recording is applied to the control circuit, and the system of the opened servo loop is stabilized. then close the servo loop to control the bias voltage, and when switching from recording to playback, open the laser power servo loop and instead apply a second preset bias voltage for playback to the control circuit. An optical recording/reproducing device further comprising a switching circuit for closing the servo loop and controlling the bias voltage after the open servo loop system is stabilized. 2. The first bias voltage set in advance for recording is set within a range corresponding to an average voltage limited by a method of modulating a recording signal. Optical recording and reproducing device. 3. At the beginning of the signal to be recorded, input a fixed pattern signal for the time until the opened servo loop system stabilizes, and set the bias voltage corresponding to the fixed pattern as the first recording bias voltage in advance. An optical recording and reproducing apparatus according to claim 1. 4. The optical recording/reproducing apparatus according to claim 1, wherein the first bias voltage set in advance for recording is controlled in accordance with the recording position on the disk.